Photo credits: math: gpointstudio, iStock Photo; beakers: agencyby, iStock Photo; jade: Kongsky, Dreamstime; garnet: Pancaketom, Dreamstime; lapis lazuli: Vladimir Blinov, Dreamstime; turquoise: Igor Sokalski, Dreamstime; sapphire: Ingemar Magnusson, Dreamstime; onyx: Igorius, Dreamstime; mashed potatoes: Stitchik, Dreamstime; bagel: Lcc54613, Dreamstime; apple: Kophoto, Dreamstime; cheese: Pavalache Stelian, Dreamstime; noodles: Davinci, Dreamstime; hummus: Elena Elisseeva, Dreamstime; lotus: Phang Kim Shan, Dreamstime; rose: Carlos Arranz, Dreamstime; bear's breech: Westhimal, Dreamstime; lily: Ahmet Gündoğan, Dreamstime; plum blossom: Levent Karaoglu, Dreamstime; school lunch: Fernando Gregory, Dreamstime; desk: Tom Wang, Dreamstime; basketballs: Denise P. Lett, Dreamstime; crocodile: Nattanan726, Dreamstime; italian wolf: Sergio Boccardo, Dreamstime; llama: Nyker1, Dreamstime; owl: Dalia Kvedaraite, Dreamstime; sheep: Gvision, Dreamstime; Peruvian mountains: Hugoht, Dreamstime; Greek landscape: Iancucristi, Dreamstime; Tuscany: Freesurf69, Dreamstime; rice terrace China: Creekmyst, Dreamstime; Iraq landscape: Bilalizaddin, Dreamstime; Cantua flower: Evie Milo, Dreamstime; ancient Egypt art: Bnzn, Dreamstime; mesopotamia: no credit given (public domain); Machu Picchu: Samantha Ong, Dreamstime; Great Wall: Trashthelens, Dreamstime; Roman mosaic: Jarcosa, Dreamstime; panda: Keith Szafranski, iStockphoto; sphinx: Javarman, Dreamstime